Integrated beamforming/rake/mud CDMA receiver architecture

ABSTRACT

A spread-spectrum demodulator architecture is presented which utilizes parallel processing to accomplish rapid signal acquisition with simultaneous tracking of multiple channels, while implementing an integrated multi-element adaptive beamformer, Rake combiner, and multi-user detector (MUD). A matched filter computational architecture is utilized, in which common digital arithmetic elements are used for both acquisition and tracking purposes. As each channel is sequentially acquired by the parallel matched filter, a subset of the arithmetic elements are then dedicated to the subsequent tracking of that channel. Additionally, multiple data inputs and delay lines are present, connecting the sampled baseband data streams of numerous RF bands and antenna elements with the arithmetic elements. The matched filter/despreader processing is virtually independent of channel origin or utilization; e.g., CDMA users, RF bands, beamformer elements, or Rake Fingers. Integration of the beamformer weighting computation with the demodulator results in substantial savings by sharing the existing circuitry performing carrier tracking and AGC. An optimal demodulator solution can be achieved through unified “space/time” processing, by providing all observables (element snapshots, Rake Fingers, carrier/symbol SNR/phase, etc.), for multiple channels, to a single adaptive algorithm processor that can beamform, Rake, and perform joint detection (MUD).

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is the subject of provisional applicationSer. No. 60/181,571 filed Feb. 10, 2000 entitled INTEGRATEDBEAMFORMING/CDMA-RAKE RECEIVER ARCHITECTURE. This application is also acontinuation-in-part application of application Ser. No. 09/707,909filed Nov. 8, 2000.

[0002] Reference is also made to Weinberg et al application Ser. No.09/382,202 filed Aug. 23, 1999 and entitled MULTI-BAND, MULTI-FUNCTION,INTEGRATED TRANSCEIVER which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] This invention relates in general to wireless communicationreceivers. In particular, it relates to the integration of multiplesignal types (CDMA, FDMA, CW, etc.), from multiple bands, with each bandand signal type potentially containing multiple user channels, and asingle receiver processing architecture with multiple antenna elementsper band for sequentially acquiring, and simultaneously demodulatingthese multiple channels, utilizing jointly-optimized advanced signalprocessing techniques of digital beamforming, Rake multipath combining,and joint detection.

[0005] 2. Description of the Prior Art Matched Filtering

[0006] A matched-filter is typically employed in a spread-spectrumdemodulator to remove the effects of PN-spreading and allow the carrierand modulating information to be recovered. The digital implementationof a matched filter can be expressed as an integrate-and-dumpcorrelation process, which is of relatively modest computational burdenduring signal tracking and demodulation. However, it is computationallyand/or time intensive to acquire such a signal, where many suchcorrelations must be performed to achieve synchronization with thetransmitted spreading sequence. For each potential code-phase offset tobe searched (which typically number in the thousands), sufficientsamples must be correlated to ensure that the integrated SNR issufficient for detection. Performed one at a time, acquisition couldeasily take several minutes to achieve in typical applications.

[0007] For applications requiring rapid signal acquisition (e.g.,seconds), a highly parallel matched-filter structure may be used tosearch many spreading code offsets simultaneously. Typically, thiscomputationally expensive apparatus would be underutilized onceacquisition is completed, during the much less demanding trackingoperation. If the same parallel matched filter is also used for trackingpurposes, only perhaps three of its numerous correlation branches(perhaps hundreds) are useful in this instance. Alternatively, it may besimpler to use a separate set of early, on-time, and lateintegrate-and*dump correlators to take over once acquisition iscomplete; in this case, the parallel matched filter would go completelyunused during tracking.

[0008] In implementations evidenced by the prior art, thematched-filtering solution has generally fallen into one of severalclasses:

[0009] 1. Slow acquisition by sequential traversal of the search spaceusing only the hardware required for tracking a signal; dedicatedhardware per channel.

[0010] 2. Rapid acquisition by parallel traversal of the search spaceusing a dedicated parallel matched filter, which is idle or shut downwhen dedicated tracking hardware takes over; dedicated hardware perchannel.

[0011] 3. Either class 1 or 2, but multi-band and/or multi-channel,using a loosely integrated but disparate collection of individualprocessing resources.

[0012] Beamforming

[0013] Beamforming is a form of spatial filtering in which an array ofsensor elements are utilized with appropriate signal processing todigitally implement a phased array antenna, for the purpose of shapingthe antenna response over time in a space-varying manner (i.e., steeringgain in some directions, and attenuation or nulls in other directions).In a radio communications system, a signal arriving at each element ofan antenna array will arrive at slightly different times, due to thedirection of arrival with respect to the antenna array plane (unless ithas normal incidence to the plane, in which case the signal will arriveat all elements simultaneously). A phased array antenna achieves gain ina particular direction by phase-shifting, or time-shifting, the signalfrom each element, and then summing them in a signal combiner. Bychoosing the relative phasing of each element appropriately, coherencecan be achieved for a particular direction of arrival (DOA), across aparticular signal bandwidth.

[0014] Digital beamforming is very analogous to this, except that thesignal on each antenna element is independently digitized, and thephasing/combining operation performed mathematically on the digitalsamples. Traditionally, digital beamforming is done on a widebandsignal, prior to despreading a CDMA waveform. This forces thecomputationally intense beamforming to take place at a much highersampling rate, resulting in more mathematical operations per second, andcorresponding increased hardware cost (there are examples addressingthis shortcoming in the prior art, such as Hanson et al., wherebeamforming is performed at baseband to avoid this and other issues).

[0015] Furthermore, digital beamforming is traditionally done as aseparate process, independent of symbol demodulation, perhaps even as aseparate product from the demodulator. In addition to the resultinginability to support advanced demodulation techniques with thisarchitecture, the cost of the beamforming function is greater as astand-alone function, compared to the incremental cost of adding thecapability to a demodulator. The largest cost-component of beamformingis the complex multiplication of each sample for each element with thebeamforming weights. When combined with the demodulator, the complexmultiply can be absorbed into computation already taking place forextremely low incremental cost due to beamforming (there is, forexample, an implementation of beamforming using digital direct synthesis(DDS) functions in the prior art, such as Rudish, et al.). Thus, whetherstand-alone beamformers merely point in the direction of the signal ofinterest, or respond more adaptively to dynamic interference conditionsby null-steering, they still lack the ability to be tightly coupled withpotential advanced demodulation techniques.

[0016] Rake Combining

[0017] Rake combining is a method of mitigating the effects of amultipath interference dominated communications channel, as is adaptiveequalization. However, in a typical equalizer, the filter time-span mustcorrespond to the multipath delay spread, and therefore tends to belimited to very close-in multipath, spanning perhaps a few symbols. TheRake, however, exploits the properties of CDMA signals (i.e., duringdespreading, all other codes become uncorrelated, including copies ofthe desired code delayed by greater than about half a chip, and arereduced to noise across the entire spread bandwidth) that enables eachmultipath component (offset by more than about half a chip) to beacquired, tracked, and despread in isolation, and then coherentlycombined. Much like beamforming, this coherent combining results inincreased effective antenna aperture and improved SNR, although usingonly a single antenna element. This divide-and-conquer approach allowsthe Rake to span an essentially arbitrary multipath delay spread,applying computational resources based linearly on the number of desireddespreader branches, or “Fingers”, desired, and not based on the delayspread itself (although acquisition time, and thus dynamic performance,is related to the actual delay spread, as this defines the limits ofwhat must be searched).

[0018] In the prior art, Rake combining is typically employed as adedicated function in a fixed CDMA receiver structure. Resources aredesigned into the receiver to perform some fixed maximum number of RakeFingers, and those resources are tied up regardless of whether thoseFingers are actually utilized or not. What is needed is a more flexibleand generalized receiver architecture, which can task resources on moreof a demand basis, and furthermore treat diversity information such asRake Fingers as simply one of several diversity inputs to be jointlyoptimized in a common process that yields maximum advantage to eachdesired user signal.

[0019] What is needed is the ability to combine potential spatialprocessing information with other dimensions of information anddiversity, both regarding the signal(s) of interest, and theinterference environment. To this end, what is needed is a receiverarchitecture for efficiently processing spatial information (antennaelements), temporal information (coherent signal multipath components;i.e., Rake Fingers), and interference information (noise powerestimates, co-channel interfering symbol soft decisions) jointly andefficiently.

SUMMARY OF THE INVENTION

[0020] The present invention applies approaches to achieve rapidacquisition in a multi-band, multi-channel signal environment, bysharing a homogeneous collection of digital processing elements. This isdone, in part, by taking maximum advantage of the computationalcommonality between the acquisition and tracking correlation processes.Furthermore, the mismatch in computational demand between acquisitionand tracking is exploited by creating a multi-channel, multi-bandintegrated receiver. Since only a small percentage of the computationalresources are consumed by tracking an individual channel, the remainingresources may be employed to accelerate the acquisition of additionalchannels. As more resources become dedicated to tracking, fewer remainfor acquisition; this has the effect of gradually reducing the number ofparallel code offsets that can be searched, gradually increasingacquisition time. In many applications, such as a GPS receiver, this isquite acceptable, as generally additional channels beyond the first fourare less urgent, and are used primarily for position refinement, andback-up signals in the event that a channel is dropped. These ideas arethe subject of U.S. patent application Ser. No. 09/707,909, filed Nov.8, 2000, entitled “Sequential-Acquisition, Multi-Band, Multi-Channel,Matched Filter”, and are preserved as features of the present invention.

[0021] The present invention embodies various extensions to thepreviously disclosed invention, wherein the multi-band capability isevolved to support multiple antenna elements at a common band (as wellas other bands), to support digital beamforming; the multi-channelcapability is evolved to support multiple Rake Fingers on a commonchannel (as well as other channels); and the multi-channel demodulatorcapability is evolved to support computationally efficient, simultaneousprocessing of all bands, elements, channels, and Rake Fingers. Thepresent invention thus forms an architectural framework capable ofhosting a variety of algorithms for joint space-time optimization ofindividual user channels in a multipath environment, as well asmulti-user (joint) detection of multiple user channels limited byco-channel interference. By considering these capabilities together,rather than as independent solutions to problems, considerableefficiencies and improvements are realized by this invention, incomparison to the prior art.

[0022] In the first aspect of the present invention, the multi-datapathreceiver architecture allows independent automatic-gain control (AGC)between multiple input bands B or elements E, minimizinginter-band/element interference, and avoiding additive noise compared toschemes that combine the bands/elements into a single signal and datastream.

[0023] To accomplish this, the present invention efficiently processesmultiple streams of W-bit complex sampled data (real data is easilyprocessed as well, by adding a complex-to-read conversion to the frontof the matched filter), so that multi-band or multi-element receiversignals can be kept spectrally separated. This concept, implementedusing D data storage paths, supports D bands and elements when shiftingat the data sampling rate (F_(samp)); alternatively, the same D datastorage paths can support D*k bands and elements by multiplexing themulti-band/multi-element streams and shifting the data at the highersampling rate of k*F_(samp).

[0024] In another aspect of the present invention, the parallelacquisition correlator, or matched-filter, aids in rapid pseudo-noise(PN)-acquisition by simultaneously searching numerous possible PN-codealignments, as compared with a less compute-intensive (but moretime-intensive) sequential search. Multiple channels of data may beco-resident in each band/element and sampled data stream using CodeDivision Multiple Access (CDMA) techniques, and multiple bands/elementsand sampled data streams share the common computation hardware in theCorrelator. In this way, a versatile, multi-channel receiver is realizedin a hardware-efficient manner by time-sequencing the availableresources to process the multiple signals, multiple antenna elements,and multiple multipath components resident in the data shift registerssimultaneously.

[0025] In still another aspect of the present invention, the matchedfilter is organized into N “Slices” of M-stages/Slice. Each Slice iscomposed further of D data paths supporting multiple bands B and/orantenna elements E. Each Slice can accept a code phase hand-off the fromthe PN-Acquisition Correlator and become a PN-tracking despreader byproviding separate outputs for early, on-time, and late correlations foreach element (with spacing depending on the sampling rate; typicallyhalf a chip). Slices are handed-off for tracking in the same directionas data flows, and correlation reference coefficients are shifted (forinstance, left to right)-this permits shifting data to be simultaneouslyavailable for the leftmost Slices that are using the data for tracking,and rightmost Slices that are using the data for acquisition. Each Slicecan choose between using and shifting the acquisition referencecoefficient stream to the right, or accepting the handoff of theprevious acquisition reference coefficient stream and using it to trackthe acquired signal.

[0026] In still another aspect of the present invention, the Acquisitioncorrelator can integrate across all available Slices to produce a singlecombined output, or the individual Slice integrations can be selectivelyoutput for post-processing in the case of high residual carrier offsetsor high-symbol rates, where the entire N*M-stage correlator width cannotbe directly combined without encountering an integration cancellationeffect. Alternatively, the Acquisition correlator can be configurable toswitch from coherent integration to non-coherent integration, by takingthe magnitude of I and Q partial integrations within the summer tree, orSlices themselves, at a point appropriate for the signal being acquired.

[0027] In yet another aspect, the present invention embodies a ScaleableAcquisition Correlator, which when tracking a maximum of G independentchannels and/or Rake Fingers, can use the remaining N-G Slices to searchfor new signals for fast re-acquisition of dropped signals, and forcontinually searching the multipath environment for Rake Fingers totrack dynamic channel conditions. Initially, Slices will be allocatedsequentially (for instance, from left to right), but after running forsome time, with signals alternately being acquired and dropped, theSlice allocation will most likely become fragmented, resulting ininefficient use of the Acquisition Correlator. This can be resolved byimplementing a de-fragmentation algorithm that swaps tracking Slicesaround dynamically to maximize the number of contiguous rightmostSlices, and thus optimize Acquisition.

[0028] In another aspect, the present invention contains G independentnumerically-controlled oscillator (NCO)-based PN-Code Generators withalmost arbitrary code rate tracking resolution (for example, better than0.0007 Hertz for a 32-bit NCO clocked at 3 MHz). All NCOs run using asingle reference clock which is the same clock that is used for allsignal processing in the Matched-Filter and Demodulator. Ultra-precisetracking of PN Code phase is maintained in the G independent phaseaccumulators. Multi-channel NCOS can in one embodiment be efficientlyimplemented by sharing computational resources and implementing phaseaccumulation registers in RAM, for the case when the processing rate isin excess of the required NCO sampling rate. Note that while eachchannel and Rake Finger requires its own PN-NCO, a single NCO is sharedacross all elements when beamforming.

[0029] In still another aspect of the present invention, the incomingwideband element data is made available to all Slices, which allows eachelement to be independently despread for each channel/Rake Finger usingthe core matched filter structure. As a result, beamforming is easilyperformed at narrowband (despread) sampling and processing rates, andwith improved potential precision. The present invention is animprovement over the prior art, because in addition to the rawcomputational savings of narrowband processing, the beamformer hardwareis time-shared across multiple elements, channels, and Rake Fingers forimproved computational efficiency.

[0030] In another aspect, the present invention allows the Beamformingcomputation to be implemented with only additional adders, due tointegration with the demodulation carrier phase rotation and the AGCscaling functions.

[0031] In yet another aspect, the present invention allows an elementsnapshot memory to operate at narrowband sampling rates, allowing aneased implementation for any snapshot operations required.

[0032] In still another aspect, integration of the beamformer with thedemodulator in the present invention allows advanced adaptive algorithmsto be implemented that can be enhanced by the feedback ofpost-demodulation metrics such as PN-SNR/phase, carrier-SNR/phase,symbol-SNR/phase, as well as error control decoding metrics.

[0033] In still another aspect of the present invention, the integratedbeamforming CDMA Rake receiver exploits both space and time diversityaspects of a multi-path environment by assigning Slices to each RakeFinger, and steering beams that individually optimize along theline-of-sight (DOA) of each multipath reflection (i.e., a potential beamfor each Rake Finger).

[0034] In another aspect of the present invention, the integratedmulti-channel demodulator and Rake combiner make coherent complex symboldata for each Rake Finger (potentially for multiple user channelssharing the same frequency band), as well as individual channels notbeing Raked, available to a single optimization process. This allows theuse of advanced multi-user detection (MUD) algorithms (e.g., jointdetection) to mitigate co-channel interference that has not beensuppressed by beamforming.

[0035] In yet another aspect, the present invention's Slice-baseddata-flow computational architecture permits dynamic, flexibleallocation of resources between tracking of multiple input bands, userchannels, and Rake Fingers, and acquisition resources for dropped/newchannels and continuously monitoring Rake dynamics.

[0036] In another aspect, the matched-filter Slice architecture of thepresent invention contains PN-tracking integrators (i.e., early,on-time, late) for each beamforming element. Furthermore, after allelements are weighted and combined, the demodulator architecture usesthe combined early/on-time/late integrations to maintain a singlePN-tracking loop for each beamforming channel, or Rake Finger.

[0037] In another aspect, the present invention allows each beamformingchannel, or Rake Finger, to combine data from all elements and form acomposite carrier and symbol discriminator that allows all elements ofthat channel to be tracked with a single carrier loop, and a singlesymbol loop.

[0038] In still another aspect, the present invention's multi-channelarchitecture allows continuous on-line element calibration capability totake place. Furthermore, calibration can be performed independently oneach user channel, and each Rake Finger, closing the calibration loopsindividually to remove essentially all bias terms.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]FIG. 1 is a generalized functional block diagram of themulti-channel matched filter architecture, illustrating the multipleinput bands, the multiple NCO-based PN Generators, and the division ofthe parallel matched filter into multiple Slices; the matched filter canbe seen to have an acquisition output, and a tracking output whichsequentially sends despread element data for each channel and eachchannel's Rake Finger into the integrated multi-channel beamformingdemodulator and Rake combiner.

[0040]FIG. 2 is a generalized functional block diagram of the matchedfilter Slice architecture (for the specific embodiment in which RAMstructures are utilized to form highly efficient data storage cells, forthe case of relatively low sampling rates); note that each Slice sharesa single PN chipping stream for despreading, and contains “E”computation elements, corresponding to the number of supportedbeamformer elements; each computation element is shared across all “M”stages/Slice.

[0041]FIG. 3 is a functional block diagram showing an example embodimentof the multi-channel, NCO-driven, PN code Generator, using efficientRAM-based state machines.

[0042]FIG. 4 is an illustration of the sequential acquisition andhandoff to tracking in the matched filter, showing how multiple antennaelements along with multiple signal bands and channels are handledsimultaneously, using an example embodiment and a time sequence ofresource allocation diagrams.

[0043]FIG. 5 is a dataflow diagram showing the complex arithmeticcalculations required to weight and combine all beamformer elements foreach despread sample coming from the matched filter.

[0044]FIG. 6 illustrates how the embodiment in FIG. 3 might producesequential despread outputs, corresponding to each band, element, andchannel (early, on-time, and late), as well as the sequence of carrierNCO outputs and beamformer weight outputs that might be produced duringthe tracking process; this figure also shows graphically how thesesequences flow through computation elements to simultaneously accomplishboth the carrier tracking and beamforming functions (no Rake in thisexample).

[0045]FIG. 7 is an illustration of the sequential acquisition andhandoff to tracking in the matched filter (similar to FIG. 4), for adifferent example embodiment containing beamforming and Rake combining,using a time sequence of resource allocation diagrams.

[0046]FIG. 8 is a functional block diagram of one embodiment of aprocessing architecture for the integrated beamforming/Rakemulti-channel demodulator, illustrating: the manner in which sequentialdata from the PN matched filter is processed to form PN, carrier, AGC,and symbol tracking loops for each channel and Rake Finger; theintegration of the carrier tracking rotation and beamforming functions;and the presentation of all channels and Rake Fingers to a singleintegrated demodulator, which can host a variety of algorithms capableof optimizing and combining same-channel multipath (Rake Fingers) andjoint detection of multiple, potentially interfering, co-channel users.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0047] The first aspect of the preferred embodiment relates to theimplementation of multiple channel, multiple frequency band receivers.At any given point in time, the state of the art in analog-to-digitalconversion (A/D) chips, and subsequent digital signal processing (DSP)technology for performing data demodulation, will allow only a certainamount of frequency spectrum (band) to be digitized into a single datastream. Within that band, multiple user channels can coexist usingvarious well known multiple-access techniques such as FDMA, TDMA, CDMA,etc.

[0048] When additional channels of interest lie outside of the frequencybandwidth that can be digitized into a single digital band, andsimultaneous reception is required from each band, then multiple RFdownconverters and A/Ds must be used to digitize multiple bands. Thepresent invention allows an arbitrary number of such bands to beprocessed together in a unified computational engine. In thisembodiment, a pool of arithmetic processing resources, or receiverchannels, can be applied on demand to various user signals, regardlessof which band they originated in. In this way, an almost arbitraryvariety and amount of frequency spectrum can be utilized, and an almostarbitrary number of user channels of varying modulation type can bedigitally extracted from it.

[0049] There are several advantages of using this technique to presentmultiple bands to a single receiver structure. Firstly, it is well knownthat as wider bandwidths containing multiple and various signals arereceived together, increasing analog fidelity requirements are imposed.This is a significant limitation, in that analog circuitry suffers fromsuch problems as intermodulation distortion (IMD), where multiplefrequency sources interact to produce distortion components. The presentinvention optimizes the analog signal fidelity by digitizingdownconverting and digitizing each band, while preserving the advantagesof a digital “software” radio-namely, integrated, flexible,multi-channel demodulation using DSP techniques.

[0050] Secondly, given an arbitrary RF and A/D dynamic range, it isdesirable to use automatic gain control (AGC) to capture the signal ofinterest within the available amplitude range of both analog circuitryand A/D converter. As wider bandwidths containing multiple and varioussignals are digitized together, they must also be subject to a commonAGC process, which will be dominated by the largest signals across allbands; this potentially decreases the SNR of the smaller signals, due toA/D quantization noise. The present invention optimizes the AGC processby allowing each band to be treated separately.

[0051] Thirdly, other schemes to digitize a composite mix of variousfrequency bands might use a technique of summing together the signalsafter translation to non-overlapping adjacent intermediate frequencies,allowing the use of a single A/D converter. In this type of scheme, thelimitations of the analog circuitry will dictate that additive noisefrom each of the various RF bands will somewhat degrade thesignal-to-noise ratio (SNR) of the resultant composite signal. Thepresent invention optimizes the SNR of each band by maintaining separateRF, IF, and digital signal paths.

[0052] Fourthly, this aspect of the present invention directly supportsdigital beamforming by utilizing this multi-band receiver technique.Since digital beamforming involves the use of a multi-element antenna,resulting in dedicated RF downconversion paths for each element, thepresent invention allows beamforming to be accommodated in a flexible,scalable fashion, by treating each element in the same manner as if itwere another signal band. Naturally, the RF implementation can in factbe simplified in comparison with the generic multi-band case, because adedicated Beamformer implementation could optimize the frequencysynthesis circuitry by using the same LO for each antenna elementdownconverter. If the beamformer combiner is implemented after thematched filter (despreader), the digital implementation is now able totreat each element as though it were just another datapath for anothersignal band.

[0053] The second aspect of implementing the preferred embodimentrelates to the architecture of the flexible computation core of thedigital matched filter. The architecture has been designed to satisfytwo different driving requirements: accelerated acquisition of a singleuser channel, and simultaneous tracking of multiple user channels.Referring to FIG. 1, front end circuitry FE provides complex basebandsamples for a plurality of frequency bands and multiple channels in theradio spectrum to an (N*M) stage data delay line (shown as beingembodied by N distinct Slices), composed of B distinct bands, each bandcomposed of E distinct elements of 2*W bits each (W bits I, W bits Qcomplex data), contains a sequence of samples of the bands of interest.It is well known that the sampling rate must be chosen to satisfy theNyquist criterion to preserve the appropriate signal bandwidth ofinterest, and to allow sufficient time resolution for acquisition andtracking; generally two or more times the chipping rate for a spreadspectrum signal. The data is then shifted through the data delay linesat the sampling rate.

[0054] For the purposes of acquisition, a single numerically controlledoscillator (PN-NCO) is needed, to serve as a finely controllable digitalfrequency source matched to the expected chipping rate of the incomingsignal. In conjunction with this, during acquisition a single PN chipGenerator is needed, to reproduce the PN sequence of the incomingsignal, at the rate dictated by the PN-NCO. This PN Sequence is thenpresented to the leftmost end of the data delay line (to the leftmostSlice), where it is also shifted from left to right down a PN sequencedelay line (shown in more detail in FIG. 2). At appropriate timeintervals, the state of the PN sequence delay line is latched into areference correlation register. The computational logic within theSlices then performs a correlation of the latched reference PN sequenceagainst the signal samples contained in the data delay line. Note thatin the example embodiment in FIG. 2, the Slice architecture isillustrated with a RAM-based implementation, which is efficient for lowsampling rates with respect to the available processing rate. Otherembodiments of the present invention might utilize a register-basedarchitecture variant, which would allow for much higher sampling rates(less than or equal to the processing rate); registers are in that caseused for all data shift-registers.

[0055] For each sample time, up to (N*M) multiplications (or N*M*E, ifelements are acquired in parallel) are performed of each data samplewith its corresponding reference PN chip (in some applications, thestages are decimated prior to performing the correlation, so that notall are tapped for computation); all of these products are then summedinto a single partial correlation value by the Acquisition SummationNetwork shown in FIGS. 1-2, which is then passed on to the demodulatorcircuitry for further integration, beamforming and Rake Finger selection(depending on the acquisition scheme chosen), thresholding anddetection. Because the data samples are shifted by one position at eachsample time, and the latched reference PN sequence is held in the sameposition over a period of time (update period), each sequential partialcorrelation within a given update period represents a differentpotential alignment (code offset) between the reference PN sequence andthe received signal. In this way, over time a correlation is performedfor all possible code offsets, to within the nearest fraction of a chipdefined by the chosen sampling rate; the timing of the latch updateperiod, and the NCO/PN-Generator code phase, are carefully controlled todetermine the specific offset search sequence. The post-processingcircuit can perform additional integrations for each code offset toachieve sufficient SNR to enable detection at the correct offset.

[0056] At this point, the receiver can be said to have completed PNacquisition, and the matched filter is able to go into PN tracking mode.During tracking, the problem is substantially easier. If there were nophase or frequency drift present, only the single correctly alignedcorrelation sequence must be computed; that would be a single multiplyand sum per input sample. Since there are phase and frequency drifts(i.e., the reference PN-NCO frequency setting becomes incorrect overtime) in typical applications, two additional correlations must becomputed as well, corresponding to the code offsets that are slightlyearly and slightly late, with respect to the currently tracked (on-time)code offset. These correlations allow the PN phase and frequency driftto be observed and tracked with the PN-NCO, using well known PN trackingloop techniques. The early, on-time, and late correlations (or partialcorrelations) are output via a separate signal path to the demodulatortracking circuitry. So, where (N*M or N*M*E) multiplies and sums must becomputed for each input sample during acquisition, only (3*E)multiply/sums must be computed for each sample during tracking. Sincethere is motivation to choose (N*M) to be as large as possible for rapidacquisition, this leaves a substantial surplus of computationalhorsepower idle during tracking.

[0057] Thus, the primary nature of the second aspect of implementing thepresent invention lies in the agility of the computational structure intransitioning, one Slice at a time, from being part of an acquisitioncorrelation process as described above, to being part of a trackingcorrelation process as described above. For the multi-channel case, thisinvolves adding additional NCO/PN-Generator pairs corresponding to thedesired number of channels and Rake Fingers (shown as G in FIG. 1) to besimultaneously tracked. Each of these creates a unique PN sequence, atunique chipping rates, and presents them to unique Slices, from left toright, as shown in FIG. 1.

[0058] Each combination of NCO/PN-Generator and Slice (matched up fromleft-to-right) form the required computational capability for tracking asingle user signal, or single Rake Finger for a single user signal. Therightmost unused NCO/PN-Generator pair, and all rightmost unused Slices,form the available computational capability for acquiring a new usersignal, and for searching for and acquiring the strongest Rake multipathcomponents. The amount of time required to acquire the new signaldepends on the number of correlation stages available, because thatdetermines the number of correlation samples that are integrated at eachsample time. All of this computation, for acquisition and tracking ofmultiple channels, happens concurrently using the flexible computationresources, and occurs transparently with respect to the multiple bandsand elements of sampled data that constantly stream through the datadelay lines. This entire process is illustrated in FIGS. 4, 6 and 7.

[0059] The third aspect of implementing the preferred embodiment relatesto the partial acquisition integration method. For the problem of PNAcquisition, it would be ideal to integrate an arbitrary number ofcorrelation samples until the appropriate SNR level is reached. However,this cannot be done in the presence of residual carrier components dueto unknown doppler and other frequency offsets, which would causeintegrations across complete carrier cycles to cancel out. In a similarmanner, integrations across multiple data symbol transitions also causescancellation. These effects limit the useful size of the acquisitionmatched filter, and would normally force much of the computationalcapabilities to go unused (through masking-out of that portion of thefilter which exceeds the appropriate integration length). This problemis mitigated in the present invention by allowing the individual Slicepartial integrations to be output to the post-processing circuitry.Various methods can be used to combine the partial integrationsnon-coherently into a complete integration while mitigating thecancellation effects.

[0060] An alternative embodiment of the present invention accomplishesthis same goal by modifying the Slice architecture slightly toincorporate the magnitude detection circuitry, or other means ofswitching to non-coherent integration, directly into each Slice. Thiswould allow each Slice to be configurable to integrate the appropriateamount of signal coherently, perform detection, and allow the summertree to perform non-coherent summation of each Slice's output, passingthat sum to the acquisition circuitry to complete theintegration/detection process.

[0061] In a fourth aspect of the present invention, the preferredembodiment employs a defragmentation algorithm to ensure that themaximum acquisition capability is maintained over time. This isparticularly important with the use of the Rake combiner functionality,as multipath components can change rather dynamically, depending on thechannel environments; acquisition resources will continually need to beavailable to monitor and acquire them. The manner of sequentialacquisition and, from left to right in FIG. 1, allocation of Slices fortracking has been described. In that initial context, the rightmostSlices are always optimally utilized for acquisition; none are wasted.However, as signals are dropped in a multiple channel trackingenvironment, holes will develop where middle Slices are no longertracking, but cannot participate in acquisition in the normal fashiondue to isolation from the rightmost Slices.

[0062] This problem is mitigated in the present invention by swappingout tracking Slices from right to left in order to maintain contiguousunused rightmost Slices for acquisition. This is done by initiallizingthe NCO/PN-Generator of the unused (left) Slice to run inoffset-synchronism with the currently tracking (right) Slice that is tobe moved; offset, in the sense that chipping frequency is identical, butcode phase is advanced by an appropriate amount to correspond with therelative difference in received signal phase at the two Slices. In unitsof time, this is basically the number of delay stages of offset betweenthe two Slices, divided by the sampling rate. At the known chippingrate, this is easily converted to a code offset. After the handoff iscomplete, the process is repeated until all tracking Slices are packedto the left.

[0063] The fifth aspect of implementing the preferred embodimentinvolves a method of using a single clocking system, synchronous to thedata sampling clock, to generate G independent NCO/PN-Generators thatproduce PN chipping sequences whose average rates can very preciselytrack the various received signal chipping rates. Also, if the NCOprocessing clock is in excess of the required NCO sampling rate,efficient RAM state storage and code phase computational hardware can betime-shared for reduced hardware size (if this is not the case, a moretraditional register-based embodiment of the NCO would be required). Ablock diagram of this concept is shown in FIG. 3.

[0064] Because each NCO is operating at the NCO sampling rate (perhapsequal to the data sampling rate), it can only make a decision to advanceto the next chip at those coarse sampling intervals. Thus, even thoughthe NCO phase accumulator knows when to advance to the next chip towithin fractions of a sampling interval, it must incorrectly wait untilthe end of the sampling interval to do so. However, this chip-jitteraverages out in the long term (as long as the NCO sampling rate isasynchronous to the chipping rate); furthermore, because the NCO clocksare all synchronous to the data sampling clocks, the jitter exactlyreflects the effective jitter that will be contained in the receivedchip transitions. In other words, both the incoming signal code phase,and the internal accumulated code phase will track very precisely; sincethey are both asynchronously sampled by data/NCO sampling clock, acommon phase jitter will be superimposed onto both, such that the jitteritself causes no additional processing loss.

[0065]FIG. 3 shows an example 6-channel implementation of the RAM-basedPN-code Generator. In this example, it is assumed that the processingclock is at least 6 times the desired NCO sampling rate. So, within thetime of each NCO sampling interval, the computational resources may becycled 6 times to produce new code phases and PN chips for each of 6channels or Rake Fingers. This allows, for example, a single adder tocompute for 6 phase accumulators. The six fractional and integer codephases are stored in RAM storage cells, and can be retrievedsequentially for processing. The new code phases are then sequentiallyupdated back into the RAMs. Also, in this example, RAM is utilized tostore the entire PN sequence for each channel. Thus, arbitrary sequencescan be generated, and the phase accumulator circuitry merely plays backthe chips at the correct rate. Alternatively, specific PN sequencegenerators could be constructed, with a slight modification of theindicated block diagram. A specific implementation requires acombination NCO/PN-Generator for each simultaneously tracked channel orRake Finger, plus an additional one for acquisition.

[0066] In the sixth aspect of the present invention, it can be seen thatthe core matched filter architecture readily supports beamformingthrough the despreading of multiple antenna elements for each signalband independently for each user channel and Rake Finger, and presentingthe narrowband data to the demodulator for weighting and combining. Thisis facilitated by first treating each antenna element as if it were justanother supported band, and passing the digitized element samples intothe multi-band matched filter. Second, the Slice architecture could thenbe configured to assign each channel-element to a unique Slice fordespreading. Such an embodiment would directly extend the previouslydisclosed architecture (U.S. patent application Ser. No. 09/707,909,filed Nov. 8, 2000) with essentially no change to the matched filteritself, but would likely require a large number of Slices to implement(#channels * #elements * #Rake-Fingers). This could also have theside-effect of increasing the relative length of the data delay lines(i.e., N*M, by increasing N).

[0067] An alternative embodiment, described here and illustrated in FIG.2, evolves the Slice architecture by despreading all elements/channel orelements/Rake-Finger within a single Slice. This has several advantages:in the first advantage, the single PN-stream needed by each element isalready available in the Slice; in the second advantage, thetime-aligned samples for each element are all available (either fromregisters, or having been read from RAM) in the same processing clockcycle for multiplication; and third, the overall Slice count and delayline length may be reduced to (#channels * #Rake-Fingers). So, in thisembodiment, each Slice requires E multipliers, and E early/on-time/lateintegrators. After a configurable amount of integration within theSlice, the stream of early/on-time/late partial integrations for eachelement are multiplexed into a sequential stream and presented to themulti-channel demodulator for further processing.

[0068] What is significant about this aspect of the present invention isits ability to reduce the beamforming computational burdenproportionally to the matched filter decimation ratio, and utilize thatadvantage by sequentially processing the despread element samples in thedemodulator. This allows the demodulator hardware to be multiplexed toaccomplish combined carrier tracking, AGC, and beamformer weighting andcombining, using minimal additional hardware resources compared to anon-beamforming demodulator. This advantage in beamforming, combinedwith the similar ease with which Rake combiner capability is also added,along with the possibility of joint processing of these functions forimproved receiver performance, represents a significant improvement overimplementations in the prior art.

[0069] The seventh aspect of the present invention is the sharing ofexisting computational resources in the demodulator to perform theactual beamforming weighting and combining functions. To form a beam ona given channel/Rake Finger, each complex sample must be multiplied bythe appropriate complex weight (to cause the desired rotation of thevector). After the weighting/rotations are performed, the complexelement samples can then be added together-the summation willconstructively combine energy for signals arriving at the antenna arrayfrom the desired direction (and sidelobes), and destructively cancelelsewhere.

[0070] A schematic dataflow diagram showing elements and correspondingweights is shown in FIG. 5, along with mathematical operations necessaryto perform beamforming. In the prior art, the physical implementation ofthis could take the form of anything from literally implementing thediagram as shown (for sampling rates equal to the processing rate), to asingle complex multiplier and two accumulators (for sampling rates muchless than the available processing rate). The innovation of the presentinvention is illustrated from a high level in FIG. 1, where the entirebeamforming operation can be seen to be absorbed into computationalready taking place in the demodulator for carrier tracking rotation,AGC scaling, and symbol integration. The only added complexity is theadditional scalar adder that rotates the carrier NCO accumulated phaseby the desired beamformer phase shift, prior to using the phase todetermining corresponding SIN/COS amplitude, as well as additionalmultiply operations per sample due to the elements (E times as manymultiplies).

[0071]FIG. 6 illustrates this in more detail, along with an exampleenumeration of the actual data operands that would flow through thisprocess (element data samples, carrier NCO samples, and beamformerweights). Whereas in the conventional implementation (FIG. 5) onlycomplex multiplies and summation are required, this technique is splitinto the beamformer rotation and the beamformer scaling as separateoperations. This is due to the manner in which this technique works.Normally, multiplication of the complex weight and the complex elementsample simultaneously rotates and scales the element I/Q vector.However, in the manner of this invention (FIGS. 1 and 6), the existingcarrier rotation circuitry is exploited to serve the additional purposeof beamforming rotation. This is done by computing the desired carrierrotation for carrier tracking (which would be constant for each elementfor a given channel/Rake Finger), but adding to that the additionalrotation desired (different for each element) for beamforming. Whilethis achieves the desired element rotation, the gain coming out of thecarrier NCO look-up table is fixed.

[0072] Thus, the scaling portion of the beamforming weighting operationis not yet done, and must be performed in a subsequent scalar multiplyon each I and Q. Conveniently, just such a function is already next inthe demodulator dataflow-the AGC function. Since software typicallyperforms both the beamformer weight calculation and the AGC scalefactor, at a relatively slow rate, the multiply is absorbed into asoftware operation to modify the AGC weight to also include thebeamformer weight, and the single pair of existing scalar multipliers isused to serve both purposes.

[0073] In the eighth aspect of the present invention, snapshots ofelement data may need to be captured for various processing to aid thebeamformer adaptive algorithms. By performing the beamforming ondespread, narrowband data, the snapshot memory functionality benefitsfrom the decimated sampling rate and potentially becomes reduced incomplexity. This may be a benefit manifested in reduced implementationcost.

[0074] In the ninth aspect, the present invention enables advancedadaptive beamforming algorithms to be implemented, through the fullintegration and tight coupling of the beamformer with the demodulationprocess. Typically, in the case of a beamformer that is more standaloneand distinct from demodulation, the beamformer would be able to point toa known signal location (DOA), and adaptively form nulls to mitigatepowerful, readily measurable sources of interference. This invention,however, makes much more information available to the beamformingalgorithm. By providing demodulator metrics to the beamformer algorithm,a closed loop is formed between demodulator performance(PN/carrier/symbol SNR/phase), and the weight adaptation process. Thisfacilitates the use of algorithms that start with known information,such as signal DOA and interference DOA, and iteratively find the bestweights that minimize the demodulator's prioritized, observable errors.Even after the symbol demodulator, error-control decoding performancemetrics can also be fed back to the optimization process.

[0075] In the tenth aspect, the present invention combines theadvantages of beamforming and Rake combining, yielding a result thatimproves SNR (actually, SINR-Signal-to-Interference-plus-Noise-Ratio,but the term SNR will continue to be used for convenience) with respectto either technique applied in isolation. By itself, beamforming isadvantageous because it simultaneously increases the effective antennaaperture in the direction of the desired signal (as well as sidelobes),while also decreasing the effective antenna aperture in otherdirections, perhaps containing interferers. With an adaptive algorithm,the beam can actually be formed to perfectly null out detectedinterferers; typically, a compromise is actually made between theseextremes, balancing desired signal gain and interfering signalattenuation.

[0076] The preferred embodiments of the present invention have theadvantage of being able to form a completely independent set of beams oneach signal channel, or on each Rake Finger of each signal channel. Thisallows each user channel the luxury of all degrees of freedom affordedby the available antenna elements to optimize its SNR. Furthermore, thisallows each multipath component to be optimized independently as well.In many environments where multipath is prevalent, each multipathcomponent (reflection) is likely to come from a different direction(DOA). Likewise, in those same environments the interference signals arelikely to be subject to the same multipath conditions, causinginterference power to be distributed among different DOAs as well. Thus,each desired signal multipath component really requires a completelydifferent beam pattern, in order to optimize its particular signal gainand interference rejection situation.

[0077] It may be the case that a large multipath component-desirable forcombining-arrives from the same direction as a strong interferencesignal. This may result in the situation where a beam pattern cannot begenerated that both passes the desired signal, and excludes theinterferer. This is an example of the strength of the jointbeamformer/Rake optimization capability afforded by the presentinvention: an intelligent algorithm in the demodulator can make use ofthe broad information presented to it to select (or iterativelydetermine based on demodulator feedback) the best combination ofmultipath elements and beam patterns to optimize demodulator SNR. Inthis example, it may be necessary to reject the multipath component fromcombining, and choose one with better spatial isolation frominterference.

[0078] In the eleventh aspect of the present invention, complex,integrated, beamformed symbol data is maintained coherently for eachchannel, and for each Rake Finger, and presented to a single-pointdetection process within the demodulator as shown in FIG. 8. Alsoavailable to this process is the integrated PN and carrier phase error,as well as information about the beamformer processing. Using thiswealth of information, a single, unified, combiner-detection algorithmcan now be used to optimize the SNR of each signal channel. Havingalready applied the benefits of beamforming to spatially isolate eachdesired incident signal component, and integrated/decimated each sampledstream to (or near) the symbol rate, it is necessary at this point inthe demodulation process to form soft symbol decisions.

[0079] Although there are many ways in which this process could becarried out, a few example methods will be outlined for clarity. In thesimplest method, samples for each Rake Finger are integrated to thesymbol level, and then delayed, weighted, and combined according tovarious combining schemes well known in the literature. Then, a softdecision is formed on the combined result and output to the next process(e.g., error control decoding).

[0080] In a more complicated method, the process just described is usedto independently form soft decisions for each of multiple signalssharing the same frequency channel (for example, co-channel signals in aCDMA system). These independent soft decisions are each corrupted by thecombined co-channel interference of all of the other channels, due toimperfect orthogonality of the spreading codes. However, the characterof the co-channel interference is now somewhat understood, having justformed soft decision estimates of each of the interferers. Thus, aprocess can now be followed to subtract the effects of the estimatedinterference from each signal, resulting in an improved estimated softdecision of each channel. Naturally, since the procedure just followedresults in improved estimates of each interferer, it can be repeated,and in fact applied iteratively until each soft decision is somewhatcleansed of the effects of the co-channel interference. This process,joint detection, is a form of multi-user detection (MUD), and is one ofmany such techniques that is well described in the technical literature.

[0081] In even more complicated methods, the MUD iterative process canbe combined with the Rake process, and perhaps even the beamformingprocess, to afford an almost arbitrary level of optimization to beachieved. What is novel in the present invention is the scalablearchitecture which efficiently processes all the available information,and makes it available to the demodulator to enable such algorithms tobe implemented. The present invention allows spatial diversity (antennaelements), time diversity (Rake Fingers), and intelligent processing ofinterference (beam patterns, co-channel joint detection) information tobe jointly optimized in a common demodulation and detection process.

[0082] In the twelfth aspect, the present invention facilitates a highlyflexible, adaptable software radio architecture that allows a fixedhardware structure of computational dataflow elements to be tasked on adynamic basis as needed. This allows the controlling software to choosehow the hardware resources are allocated between the number of userchannels, the number of channels supporting Rake, the number of RakeFingers per channel (could be different on each channel), and the lengthof the acquisition matched filter. Furthermore, the actual processingcapacity of this architecture really depends on the relationship betweenthe extent of physical resources actually committed (e.g.,#multipliers/Slice, or #Slices), the maximum processing clock ratesupported by the implementing technology, and the desired input datasampling rate-therefore, an embodiment of this invention could allow theaforementioned features to be further traded-off against input samplerate. Note that yet another related consideration is the relationshipbetween the number of bands and elements, and the number of datapathsthat an embodiment implements-if there are more elements and bands thandatapaths, the effective sampling rate must be increased to accommodatemultiplexing. Thus, the present invention enables the dynamic tradeoffof all these features and issues, which represents a clear improvementover the prior art, and which is much needed in the rapidly evolving andcomplex wireless communications field.

[0083] In the thirteenth aspect, the preferred embodiment of the presentinvention incorporates all elements for a given channel or Rake Fingerdirectly into the Slice architecture, rather than treating each elementas if it were an independent channel (as the Rake Fingers are treated bythe matched filter). While either of these methods could be chosen toimplement a specific embodiment under this invention, there areadvantages to the former method, as illustrated in FIG. 2. Specifically,by incorporating the despreading of all elements for a given channel orRake Finger into the same Slice, the integrations remain exactlytime-aligned, which is required for coherent beamforming (while thiscould certainly still be satisfied in other embodiments, such as oneelement per Slice, the timing and control problem is more complicated).The dataflow control within the Slice is also simplified, because eachelement sample is automatically available in parallel for multiplicationby the PN sequence. Furthermore, each element shares the samePN-Generator in a direct and convenient fashion, because the PN codephase misalignment on each element due to the angle of arrival at theelement array should in most cases be negligible compared with thelength of each chip.

[0084] In addition, another benefit to this aspect of the presentinvention lies in the ability to obtain the benefit of beamforming gainon the early and late error integrations. By rotating and combining theearly/late outputs from each element, a single, coherent PN code phaseerror is generated, which is used to correct a single PN-tracking loopfor each channel or Rake Finger.

[0085] In the fourteenth aspect of the present invention, thearchitecture of the preferred embodiment allows a single carriertracking loop and a single symbol tracking loop to track all of theelements for a channel or Rake Finger. This is similar to the single PNtracking loop just described. The reduction in the number of trackingloops is useful in minimizing the demodulator complexity.

[0086] In the fifteenth aspect, the present invention represents asubstantial improvement over implementations described in the prior art,particularly with respect to the calibration problem. In the ideal case,the geometry of the antenna array would be precisely known, each antennaelement would exhibit identical performance characteristics, and theentire RF downconversion path through the A/D converters would haveidentically matched delay and other attributes. Furthermore, thisperfection of array and element pathways must be maintained over time,temperature, and other variations. It is well known that this can onlybe achieved with limited precision, and that the resulting mismatcherrors will severely degrade the ability to form a coherently phasedbeam. As a result, element calibration is required.

[0087] To calibrate the array and element pathways, a commonly usedtechnique is to generate a reference signal at the center frequency ofthe array, and couple this reference signal into the receiver antennaelements such that a known and fixed angle of incidence (DOA) isachieved. Resources are then allocated within the beamformer hardware tomeasure the phase of the reference signal after propagating through theentire RF pathway for each element. In this way, the relative phaseerror for each element path can be measured over time. Once the phasemismatches are known, a calibration vector is formed which is embeddedin the beamformer weight calculations in such a way as to remove most ofthe effects of the mismatch from the beamforming process. Thiscalibration vector must be updated periodically to keep up with changesin the mismatch between elements. In some cases, this calibration methodis sub-optimal, because it ignores any dispersive effects of theatmosphere that may slightly skew the signal arriving at each element.

[0088] In the present invention, the calibration process is greatlysimplified and improved. In fact, due to the integration of thebeamformers with the demodulators for each channel and Rake Finger,calibration can be done for each antenna element signal path in theabsence of any additional calibration signal, and without consuming anyadditional matched filter or demodulator processing resources.Furthermore, calibration can be performed independently on each signalchannel or Rake Finger, taking into account any atmospheric distortionsthat may distinguish their different propagation pathways. Finally, thisprocess of calibration actually closes a loop between the beamformingprocess, and the integrated carrier error terms on a per elementbasis-the residual carrier phase error resulting from imperfections inpointing the beamformer are systematically forced to zero as a result.Thus, the complexity of calibration is reduced, no additional hardwareis required, and the quality of calibration becomes nearly perfect, on aper-signal basis.

[0089] The way that this calibration is implemented, at essentially zeroincrease in cost, is once again due to the way the present inventionembeds all despread element information with the demodulator, where theactual beamforming weighting and combining occurs. In the normaloperation of the present invention, the element rotation complexmultiplication occurs sequentially on an element by element basis,followed by the scalar magnitude multiplication, after which theproducts are combined by integrating and dumping in an accumulator (seeFIGS. 1 and 6). In normal operation, only the combined weighted elementsare subsequently used for symbol demodulation, and only a single PN,symbol, and carrier tracking loop is formed. As a result, the individualrotated element samples are not needed. However, those individualrotations are actually calculated, and can be saved and integrated foran arbitrary amount of time to achieve an extremely accurateaccumulation of residual carrier phase error per element. If thepointing were perfect, the integrated error would approach zero. Anynon-zero residue represents calibration error for that element, whichcan now be corrected and fed back to the weights. The only additionalcost associated with this calibration process is additional memory orregisters to store the per-element integrations, and an additional adderto perform the sequential integration.

[0090] The previous description of the preferred embodiments is providedto enable any person skilled in the art to make or use the presentinvention. The various modifications to these embodiments will bereadily apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other embodiments without the use ofthe inventive facility. Thus, the present invention is not intended tobe limited to the embodiments shown herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A multiple frequency band, multiple channel radio receiver comprising a front end circuitry for providing complex base band samples for a plurality of frequency bands and multiple channels in digital format, a parallel digital matched filter in which common digital arithmetic elements are used for both acquisition and tracking purposes connected to said front end circuitry, said matched filter being arranged to perform a plurality of simultaneous correlations of received spread spectrum signals against selected replica offsets of a spreading sequence, said parallel digital matched filter providing N slices with M stages per slice and W bit data quantization, each slice being adapted to perform 1/N of the acquisition computation and then is handed off to become a dedicated tracking module for one channel, respectively, and an integrated multi-element adaptive digital beamformer combiner connected to said parallel digital matched filter.
 2. The multiple frequency band, multiple channel radio receiver defined in claim 1 wherein said matched filter includes an N*M stage data delay line composed of B distinct bands, each band being composed of E distinct elements of 2*W bits each and a single numerically controlled oscillator to serve as a control digital frequency source matched to the expected chipping rate of the incoming signal.
 3. The multiple frequency band, multiple channel radio receiver defined in claim 1 including a Rake Combiner for mitigating the effects of multipath interference dominated communication channels connected to said parallel digital matched filter.
 4. A multiple frequency band, multiple channel radio receiver comprising a front end circuitry for providing complex base band samples for a plurality of frequency bands and multiple channels in digital format, a matched filter in which common digital arithmetic elements are used for both acquisition and tracking purposes connected to said front end circuitry, said matched filter being arranged to perform a plurality of simultaneous correlations of received spread spectrum signals against selected replica offsets of a spreading sequence, said parallel digital matched filter providing N slices with M stages per slice and W bit data quantization, each slice being adapted to perform 1/N of the acquisition computation and then is handed off to become a dedicated tracking module for one channel, respectively, and integrated multi-element adaptive digital beamformer and Rake Combiners connected to said matched filter.
 5. The multiple frequency band multiple channel radio receiver defined in claim 4 including a multi-channel demodulator connected to said matched filter for simultaneously processing all bands, elements and channels and Rake Fingers.
 6. A multiple frequency band, multiple channel radio receiver comprising a front end circuitry for providing complex base band samples for a plurality of frequency bands and multiple channels in digital format, a matched filter in which common digital arithmetic elements are used for both acquisition and tracking purposes connected to said front end circuitry, said matched filter being arranged to perform a plurality of simultaneous correlations of received spread spectrum signals against selected replica offsets of a spreading sequence, said parallel digital matched filter providing N slices with M stages per slice and W bit data quantization, each slice being adapted to perform 1/N of the acquisition computation and then is handed off to become a dedicated tracking module for one channel, respectively, including a multi-channel demodulator processor connected to said matched filter for simultaneously processing all bands, elements and channels, and to function as an integrated multi-element adaptive digital beamformer combiner.
 7. The multiple frequency band, multiple channel radio receiver defined in claim 6 wherein said multi-channel demodulator processor includes a defragmentation module to insure the maximum acquisition capability of said receiver is maintained over time.
 8. The multiple frequency band, multiple channel radio receiver defined in claim 6 including a single clocking system synchronous to a data sampling clock for generating G independent NCO/PN-generators that produce PN chipping sequences whose average rates can precisely track the various received signal chipping rates, respectively.
 9. The multiple frequency band, multiple channel radio receiver defined in claim 6 wherein said multi-channel demodulator processor is adapted to form a completely independent set of beams on each single channel on each Rake Finger of each signal channel.
 10. The multiple frequency band, multiple channel radio receiver defined in claim 6 wherein as each channel is sequentially acquired by said matched filter, and said demodulator processor assures that common digital arithmetic elements are used both for acquisition and tracking purposes, respectively.
 11. The multiple frequency band, multiple channel radio receiver defined in claim 6 wherein multiple data inputs and delay lines are present and are available for processing at each arithmetic element so that the matched filter/despreader processing is virtually independent of channel origin (e.g. CDMA users, beamform element, or Rake Fingers).
 12. The multiple frequency band, multiple channel radio receiver defined in claim 6 wherein there is a common NCO/PN-generator within a common beamformer element set.
 13. A multiple frequency band, multiple channel radio receiver comprising a front end circuitry for providing complex base band samples for a plurality of frequency bands and multiple channels in digital format, a parallel digital matched filter in which common digital arithmetic elements are used for both acquisition and tracking purposes connected to said front end circuitry, said matched filter being arranged to perform a plurality of simultaneous correlations of received spread spectrum signals against selected replica offsets of a spreading sequence, said parallel digital matched filter providing N slices with M stages per slice and W bit data quantization, each slice being adapted to perform 1/N of the acquisition computation and then is handed off to become a dedicated tracking module for one channel, respectively, including a multi-channel demodulator processor connected to said matched filter for simultaneously processing all bands, elements and channels, and to function as an integrated multi-element multi-user detector.
 14. The multiple frequency band, multiple channel radio receiver defined in claim 13 wherein said matched filter includes an N*M stage data delay line composed of B distinct bands, each band being composed of E distinct elements of 2*W bits each and a single numerically controlled oscillator to serve as a control digital frequency source matched to the expected chipping rate of the incoming signal.
 15. The multiple frequency band, multiple channel radio receiver defined in claim 13 including a Rake Combiner for mitigating the effects of multipath interference dominated communication channels connected to said parallel digital matched filter.
 16. The multiple frequency band multiple channel radio receiver defined in claim 15 including a multi-channel demodulator connected to said matched filter for simultaneously processing all bands, elements and channels and Rake Fingers.
 17. The multiple frequency band, multiple channel radio receiver defined in claim 16 wherein said multi-channel demodulator processor includes a defragmentation module to insure the maximum acquisition capability of said receiver is maintained over time.
 18. The multiple frequency band, multiple channel radio receiver defined in claim 13 including a single clocking system synchronous to a data sampling clock for generating G independent NCO/PN-generators that produce PN chipping sequences whose average rates can precisely track the various received signal chipping rates, respectively.
 19. The multiple frequency band, multiple channel radio receiver defined in claim 13 wherein said multi-channel demodulator processor is adapted to form a completely independent set of beams on each single channel on each Rake Finger of each signal channel.
 20. The multiple frequency band, multiple channel radio receiver defined in claim 13 wherein as each channel is sequentially acquired by said matched filter, and said demodulator processor assures that common digital arithmetic elements are used both for acquisition and tracking purposes, respectively.
 21. The multiple frequency band, multiple channel radio receiver defined in claim 13 wherein multiple data inputs and delay lines are present and are available for processing at each arithmetic element so that the matched filter/despreader processing is virtually independent of channel origin (e.g. CDMA users, beamform element, or Rake Fingers).
 22. The multiple frequency band, multiple channel radio receiver defined in claim 13 wherein there is a common NCO/PN-generator within a common beamformer element set. 